Method of making electrically insulated copper strip conductors



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July 15, 1969 E. H. OLSON 3,455,021

METHOD OF MAKING ELECTRICALLY INSULATED COPPER STRIP CONDUCTORS OriginalFiled Sept. 14, 1964 I I A 1 I L.

United States Patent 3,455,021 METHOD OF MAKING ELECTRICALLY INSU- LATEDCOPPER STRIP CONDUCTORS Emil H. Olson, Muskegon, Mich., assignor toAnaconda Wire and Cable Company, a corporation of Delaware Originalapplication Sept. 14, 1964, Ser. No. 396,087, now Patent No. 3,317,876,dated May 2, 1967. Divided and this application Mar. 6, 1967, Ser. No.644,036

Int. Cl. H01f /06; C23b 5/58 US. Cl. 29-605 15 Claims ABSTRACT OF THEDISCLOSURE A method of making electrically insulated copper stripconductors by applying metallic aluminum to the side edges of the copperstrip, then treating the metallic aluminum on the side edges to form acontinuous oxidic dielectric film thereon and finally coating at leastone of the flat surfaces of the strip with an electrically insulatedfilm.

This i a division of copending application Ser. No. 396,087, filledSept. 14, 1964 and now Patent No. 3,317,876.

The invention relates to electrically insulated copper strip conductorsfor use in the manufacture of electrical coils. More particularly, it isdirected to a method of manufacturing electrically insulated copperstrip conduc tors which are characterized by metallic aluminum along theside edges of the strip and have a dielectric oxidic coating on themetallic aluminum.

In the manufacture of insulated copper magnet strip conductor which aremost commonly used for the manufacture of electrical coils, it isessential that the insulating coatings which are applied to the copperstrip be free from discontinuities which might cause short circuits intheir electrical application. The most common source of thesediscontinuities in the insulating coating has-been found to occur alongthe side edges of the strip conductor.

These side edges are the most common source of failings both becausethey are so diflicult to coat properly with insulating varnishes orlacquers and also because they present such a relatively sharp edge thatthe insulating coatings either do not adhere properly or they becomescraped off during handling, such as the winding operation required toform electrical coils.

In forming the narrow copper strips in the fabrication of the stripconductors, the method almost universally followed is to cut the narrowcopper strip from a much wider copper strip. When this wide copper stripis cut longitudinally into narrower strips the cutting operation alwaysexposes the side edge portions of the narrower strips and leaves themrough with slivers and burrs. Thus, even if the wider copper strips arecoated with a dielectric insulating coating before the cuttingoperation, the flat surfaces may be adequately insulated but the sideedge portions must be covered over with a suitable insulation or theywould surely be the source of a short circuit particularly in their useof electrical coils.

It is an object of the invention to provide continuous methods for themanufacture of these electrically insulated strip conductors.

The method is one for making an electrically insulated copper stripconductor in which a relatively wide strip of copper i cut into aplurality relatively narrow strips which are each bare of any coating attheir side edges. According to the invention, the side edges of thenarrow strips are cleaned and deburred and metallic aluminum is appliedto the side edges. The strip is then treated to form a continuous oxidicdielectric film on the metallic aluminum along the side edges to coverand insulate the side edges of the strip. An electrical insulating filmcoating is also provided on at least one of the flat surfaces of thestrip. It is clear that by the method of the invention in which the sideedges of metallic aluminum are first coated, the subsequent formation ofan oxidic dielectric film is easily made to the metallic aluminum and astrong and continuous insulating film along the side edge portions ofthe strip conductor is assured. The coating of the flat surfaces of thestrip conductor can be made either before the strip conductor has beenlongitudinally cut from a wider copper strip or it can be madesubsequent to the formation of the dielectric oxidic film along the sideedges of the strip.

The metallic aluminum can be applied to the side edges of the stripeither by passing the strip continuously through an aluminum coatingoperation or the copper strip can be wound into a roll and coated withaluminum along its side edges in a batch process. For the formation ofthe dielectric oxidic film on the aluminum along the side edges,however, it is preferred first to wind the copper strip into roll formwith a sealant between the turns of the roll and then immerse the rollinto an aqueous electrolytic oxidation bath to form an anodic dielectricfilm on the metallic aluminum which is contained on the side edges ofthe copper strip. Once the copper strip conductor has been coated on itsside edges with the oxidic dielectric film, and provided at least one ofthe fiat surfaces is coated with an electric insulating film, theelectrically insulated copper strip conductor can be unwound from theroll and then wound into an electrical coil.

A preferred embodiment of the invention described hereinbelow withreference to the drawing wherein:

FIG. 1 is a side elevation, partly schematic, of a first method offorming electric strip conductors;

FIG. 2 is a side elevation, partly schematic, of a second method offorming electric strip conductors; and

FIG. 3 is a section of a copper strip conductor formed according to themethods in FIGS. 1 and 2.

As shown in FIG. 1 a coil 10 comprising a multiplicity "of turns of afiat strip of copper 11, which has been cut from a wider copper strip,is being fed to a first cleaning and deburring station 12 where the sideedge portions 13 of the strip 11 are being cleaned of slivers and burrsby means of vertical rolls 14 and horizontal rolls 15. By thesemechanical means or their equivalent, the sharp cutting edges of thestrip 11 are rounded and relatively smooth side edges are prepared bythis mechanical treatment and with the assistance of a chemicaltreatment if required. The cleaned and deburred copper strip 11 is thenpassed to a chamber 16 where metallic aluminum is disposed only on theside edges of the copper strip. Protective plates 17 and 18 arepositioned substantially against the flat surfaces of the strip 11 toprotect these flat surfaces from aluminum deposition. These protectiveplates should be of a material such as plastic, wood or fiber. Inapplying the aluminum coating 19 on the side edges of the strip of thecoating generally disposed not only along the side edge portions of thestrip but also along a small marginal edge portion of the flat surfacesof the strip as will be seen in FIG. 3. Thus, in FIG. 1 as the copperstrip 11 emerges from the aluminum coating chamber 16 the strip 11appears to have a greatly enlarged thickness and this has been done toillustrate that an aluminum coating 19 has been disposed on the sideedges of the strip and on a small marginal portion of the fiat surfacesof the strip.

The copper strip with the aluminum disposed on its side edges is thenpassed to a coating station 20 where an organic insulating film such asepoxy, Formvar, polyester, polyurethane, polyamide, polyirnide,polyamidepolyimide, or any of the standard materials now used forcoating magnet conductors, is applied to the fiat surfaces of the strip11 between the aluminum deposit 19 on the side edges thereof.

The thus coated strip conductor is then wound into a roll While a thinplastic sheet 21 is simultaneously fed with the strip conductor 11 sothat the roll is interleaved with this thin plastic sheet 21 betweensuccessive turns. Polyethylene sheets have been used with success forthis operation and it has been found that the rolls can also beinterleaved with another sealant such as a heavy liquid like kerosene.

The roll 22 and others like it are then taken to anodizing equipmentWhere they are lowered into an electrolytic bath 23 which may bechromic, sulfuric, oxalic or other acid or it may be a caustic alkalinebath. Low voltage direct current is then passed through the bath witheach of the rolls therein serving as the anode. A lead stainless steelor other conducting electrode is employed as the cathode. A film ofaluminum oxide is thereby formed on any aluminum surface exposed to theelectrolyte and thus all exposed aluminum edges defining the flat sidesof the rolls are covered with an even and continuous insulating anodicfilm.

The plastic sheet 21 which is interleaved between the turns of the rollserves as a sealant to prevent the electrolyte from penetrating betweenthe turns of the roll by capillary action where if it remains it mightcorrode the copper if it were to contact the metal or it would attackthe organic coating which has previously been applied to the flatsurfaces of the strip conductor. After the anodizing has been completedthe batch of rolls are lifted from the bath, rinsed and dried and thestrip conductor is then prepared to be rewound from the roll intoelectrical coils to which leads may be attached.

Referring now to FIG. 2 a second embodiment of the method of theinvention is shown schematically. A roll 25 of bare copper stripconductor which has been cut from a wider copper strip but has had noprior treatment is interleaved with a sealant, either a thin plasticsheet or a heavy liquid. The roll 25 is immersed into an etchingsolution in bath 26 to clean the edges and remove burrs, slivers andsharp corners along the side edges of the narrow copper strip. Thesealant will prevent the solution in the bath from being drawn betweenthe turns of the roll by capillary action and will maintain the flatsurfaces free from this etching opertaiou. The etched roll 25 is thenremoved from the bath 26 and is moved to a chamber 27 where the roll 25is placed and the side edges of the entire interleaved coil for metallicaluminum deposit thereon by any of the presently known methods such asvapor deposition, plating, cladding or perhaps an electrochemicalprocess. The roll 25 is then passed to an anodizing bath 28 where thealuminum coated side edges can be anodized to form an anodic dielectricfilm on the aluminum side edges by immersing the roll 25 into theelectrolyte in a similar operation as that described in relation toFIG. 1. A copper strip conductor 29 is then unwound from the roll 25 andis passed through a coating die 30 where any of the organic insulatingfilms mentioned above are coated either on one flat surface of the stripconductor, both flat surfaces, or on the entire conductor.

The conductor 29 is then passed to a coil winding operation where theextended length of copper strip conductor is wound into a multilayercoil with the organic electric insulating film disposed within succesivelayers of the coil, and then suitable leads are attached.

It is also proposed that the copper strip conductor can be formed bycoating the entire copper strip with metallic aluminum coating and thenanodizing the entire aluminum coated copper strip.

As shown in FIG. 3 the electrically insulated copper strip conductorconsists of a copper strip 31 which has a top flat surface 32 and abottom flat surface 33 and fiat side edge portions 34 and 35. A metallicaluminum coating is deposited on the flat side edges 34 and 35 andextends continuously beyond the side edges and covers the marginal edgeportions 36, 36, 37 and 37' on both of the fiat surfaces up to about 10percent of the flat surface area. A thin organic insulating film 38 and39 is deposited on the fiat surface of the copper strip conductorbetween the aluminum side edge deposits 36, 36, 37 and 37.

I claim:

1. A method of making an electrically insulated copper strip conductorin which a relatively wide strip of copper is cut into a plurality ofrelatively narrow strips which are each bare of any coating at theirside edges comprising:

(a) cleaning and deburring the side edges of said narrow strip,

(b) applying metallic aluminum to said side edges,

(c) treating the metallic aluminum on the side edges to form acontinuous oxidic dielectric film thereon to cover and insulate the sideedges of the strip, and

(d) coating at least one of the fiat surfaces of the strip with anelectrical insulating film.

2. A method of making strip electrical coils from an electricallyinsulated copper strip in which a relatively wide strip of copper is cutinto a plurality of relatively narrow strips which are each bare of anycoating at their side edges comprising:

(a) cleaning and deburring the side edges of said narrow strip,

(b) applying metallic aluminum to said side edges,

(c) treating the metallic aluminum on the side edges to form acontinuous oxidic dielectric film thereon to cover and insulate the sideedges of the strip,

(d) coating at least the fiat surfaces of the strip with an electricalinsulating film, and

(e) winding the resulting insulated copper strip into an electricalcoil.

3. A method of making an electrically insulated copper strip conductorin which a relatively wide strip of copper is cut into a plurality ofrelatively narrow strips which are each bare of any coating at theirside edges comprising:

(a) cleaning and deburring the side edges of said narrow strip,

(b) applying metallic aluminum to said side edges,

(c) treating the aluminum coating on the side edges by subjecting thestrip to anodic oxidation to form a continuous anodic dielectric film onthe aluminum metal to cover and insulate the side edges of the strip,and

(d) coating at least one of the flat surfaces of the strip with anelectric insulating film.

4. A method of making an electrically insulated copper strip conductorin which a relatively wide strip of copper is cut into a plurality ofrelatively narrow strips which are each bare of any coating at theirside edges comprising:

(a) etching the side edges of the strip to clean and deburr it,

(b) applying metallic aluminum only to substantially the side edgeportions of the strip and leaving the flat surfaces of the strip freefrom metal aluminum except along the marginal edge portions thereof,

(c) immersing the copper strip coated at its side edges with metalaluminum into an aqueous electrolytic oxidation bath to form acontinuous anodic dielectric film on the aluminum metal to cover andinsulate the side edges of the strip, and

(d) coating at least one of the flat surfaces of the strip with anelectric insulating film.

5. A method of making an electrically insulated copper strip conductorin which a relatively wide strip of copper is cut into a plurality ofrelatively narrow strips which are each bare of any coating at theirside edges comprising:

(a) cleaning and deburring the side edges of the narrow strip,

(b) continuously applying metallic aluminum to the side edges of saidnarrow strip,

(c) winding the strip into a roll with a sealant between turns thereofin which the aluminum side edges of the narrow strip are exposed at theend faces of the roll,

(d) treating the end faces of the roll to form a continuous oxidicdielectric film on said aluminum edges, and

(e) coating at least one of the fiat surfaces of the strip with anelectric insulating film.

6. A method according to claim 5 wherein said fiat surfaces of the stripare protected during application of aluminum metal so that the metalaluminum is formed on the side edges thereof.

7. A method according to claim 5 wherein said sealant is a plastic film.

8. A method according to claim 5 wherein said sealant is a heavy liquid.

9. A method according to claim 5 wherein the roll is immersed into anaqueous electrolytic oxidation bath to form a continuous anodicdielectric film on the aluminum metal to cover and insulate the sideedges of the strip.

10. A method of making strip electrical coils from an electricallyinsulated copper strip in which a relatively wide strip of copper is cutinto a plurality of relatively narrow strips which are each bare of anycoating at their side edges comprising:

(a) cleaning and deburring the side edges of the narrow strip,

(b) continuously applying metallic aluminum to the side edges of saidnarrow strip,

(c) winding the strip into a roll with a sealant between turns thereofin which the aluminum side edges of the narrow strip are exposed at theend faces of the roll,

(d) treating the end faces of the roll to form a continuous oxidicdielectric fihn on said aluminum edges,

(e) coating at least the flat surfaces of the strip with an electricinsulating film, and

(f) winding the resulting insulated copper strip into an electricalcoil.

11. A method of making an electrically insulated copper strip conductorin which a relatively wide strip of copper is cut into a plurality ofrelatively narrow strips which are each bare of any coating at theirside edges comprising:

(a) winding the strip into a roll with a sealant between turns thereofin which the bare edges of the narrow strip are exposed at the end facesof the roll,

(b) cleaning and deburring the bare edges of the roll,

(c) applying metallic aluminum to the bare edges at the end faces of theroll,

(d) treating the end faces of the roll to form a continuous oxidicdielectric film on said aluminum edges, and

(e) coating at least one of the fiat surfaces of the strip with anorganic electric insulating film.

12. A method according to claim 11 wherein said sealant is a plasticfilm.

13. A method according to claim 11 wherein said sealant is a heavyliquid.

14. A method according to claim 11 wherein the roll is immersed into anaqueous electrolytic oxidation bath to form a continuous anodicdielectric film on the aluminum metalv to cover and insulate the sideedges of the strip.

15. A method of making strip electrical coils from an electricallyinsulated copper strip in which a relatively wide strip of copper is cutinto a plurality of relatively narrow strips which are each bare of anycoating at their side edges comprising:

(a) winding the strip into a roll with a sealant between turns thereofin which the bare edges of the narrow strip are exposed at the end facesof the roll,

(b) cleaning and deburring the bare edges of the roll,

(c) applying metallic aluminum to the bare edges at the end faces of theroll,

((1) treating the end faces of the roll to form a continuous oxidicdielectric film on said aluminum edges,

(e) unwinding the edge insulated strip from the roll,

(f) coating at least one of the fiat surfaces of the strip with anorganic electric insulating film, and

(g) winding the resulting insulated copper strip.

References Cited UNITED STATES PATENTS 2,974,097 3/1961 Ramirez et al204-28 3,061,527 10/ 1962 Karner et al. 204-15 3,223,896 12/1965 Smithl74-119 3,270,401 9/1966 Staley et al 29-605 FOREIGN PATENTS 908,330 10/1962 Great Britain.

JOHN H. MACK, Primary Examiner T. TUFARIELLO, Assistant Examiner U.S.Cl. X.R. Z04-15, 28

